DENSITY-FUNCTIONAL THEORY OF THE WATER LIQUID-VAPOR INTERFACE .2.

An improvement of our previous extended mean-field theory of the liqui d-vapour interface of water is described. This revision extends the ra nge of validity of the theory to room temperature. The current theory is improved in three aspects: (1) the effective angle-averaged pair po tential is obtained by the RAM (reference-averaged Mayer) function app roximation, avoiding expansion in inverse powers of temperature; (2) d ie soft repulsive core of the TIP4P water model pair potential is trea ted accurately; and (3) the anisotropic interactions are represented b y a higher-order (l = 5) multipole expansion. The current theory inclu des no adjustable parameters; the critical temperature T(c) is found t o be 609 K. Detailed calculations are given for room temperature, wher e molecular-dynamics simulation results are available for comparison. A more detailed representation of the orientational distribution funct ion is reported.